In recent years, development of technology seeking to reduce power consumption of a memory system by replacing a volatile memory (SRAM and DRAM) constituting the memory system mounted in electronic devices such as computers, mobile phones, and digital cameras with a nonvolatile memory is under way. According to the technology, data will not disappear after power is turned off and thus, for example, power consumption during standby excluding the data processing time can be reduced to almost zero.
A leading candidate for a nonvolatile semiconductor memory in place of a volatile memory in a memory system is a magnetic random access memory (MRAM). This is because, when compared with other nonvolatile semiconductor memories, the magnetic random access memory excels at memory characteristics such as high-speed operation and the number of times of data rewritability.
On the other hand, depending on memory system specifications, it is desirable to use a volatile memory as a cache memory or main storage memory as before and to use the magnetic random access memory as an alternative to a storage device such as a NAND flash memory and HDD.
Thus, under the current circumstances, whether to use the magnetic random access memory as a cache memory or main storage memory, or as a storage device (file memory) is determined in accordance with memory system specifications.
For example, while it is important to seek lower power consumption during reading when the magnetic random access memory that frequently executes a read operation is developed as a cache memory or main storage memory, it is important to seek lower power consumption during writing if the magnetic random access memory is developed as a storage device.
Therefore, when the magnetic random access memory is developed as an alternative to a cache memory or main storage memory, if the magnetic random access memory is used as a storage device, a problem of increased power consumption during writing is caused. Conversely, when the magnetic random access memory is developed as an alternative to a storage device, if the magnetic random access memory is used as a cache memory or main storage memory, a problem of increased power consumption during reading is caused.